Synthetic Photochemistry. LIV. The Photoaddition Reaction of Methyl 2,4-Dioxopentanoate with 2,5-Dimethyl-2,4-hexadiene, a Sterically Crowded Conjugated Diene
The photoadditionreaction of methyl 2,4-dioxopentanoate with 2,5-dimethyl-2,4-haxadiene gave a normal [2+2]adduct in only a small amount, but three isomeric dihydropyrans (4–6), two oxetanes (7 and 8), and five isomeric hydroxy keto esters (9–13). The mechanism and regioselectivity were discussed.